Question
A sphere cannot roll on:
  1. A smooth horizontal surface.
  2. A smooth inclined surface.
  3. A rough horizontal surface.
  4. A rough inclined surface.

Answer

  1. A smooth horizontal surface.
  2. A smooth inclined surface.

Explanation:

A sphere cannot roll on a smooth inclined surface and on a smooth horizontal surface because there is no backward force (force of friction) to prevent its slipping.

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